FEFFLAP: A Finite Element Program for Analysis of Fluid-Driven Fracture Propagation in Jointed Rock. Volume 1. Theory and Programmer's Manual

摘要

FEFFLAP (Finite Element Fracture and Flow Analysis Program) is a finite element program for two-dimensional analysis of static or quasi-static propagation of discrete fractures in homogeneous or jointed media. The fractures, or cracks, can be driven by a variety of loading conditions, including internal fluid pressure. The code contains quite sophisticated fracture mechanics: stress intensity factors are calculated with special crack tip finite elements; fracture instability and angle of propagation are estimated from any one of three fracture criteria; induced cracks can change direction and can interact with pre-existing fractures. FEFFLAP also provides for non-linear behavior of discontinuities such as geologic interfaces and joints, and for steady-state viscous fluid flow in the cracks and the discontinuities. The program is both incremental and iterative. FEFFLAP can calculate the exact load required to initiate or extend any crack. A multiple load capability is available in the code, for complicated fracturing problems involving simultaneously loads that can change and loads that do not change. The operation of the code depends heavily on graphics because it is a fully interactive model. The code can accommodate up to 10 different materials and can propagate up to 9 cracks at a time; these numbers can be increased with minimal modifications. This report describes the theory underlying the code. The logic of the program is also given in some details to enable potential users to make modifications and additions, as well as to facilitate transfer of the current version, developed on a CRAY, to other machines. 44 references, 26 figures, 7 tables. (ERA citation 10:019915)